One advantage to having multiple fleets is you probably have enough miniatures to put on a game at a club with exclusively your own toys. (I sometimes do that with Full Thrust and Pulp Alley. Keep trying to convert more friends to my game systems of choice.)
What what? Moaning? I'll have you know that's not moaning, it's harping!
I have an idea. How about we play a game of Full Thrust with your BFG and my Space Fleet miniatures?
Happy to learn BFG if you happen to bring it to a games event I can manage to attend. I may have to see if a local gaming friend who likes Space Fleet, Full Thrust, and BFG is interested in teaching me. (At the moment he's trying to make space carrier rules for his BFG proxies to use in Full Thrust. And I'm more than happy to help him break all three games at once.)